Preservation and accessibility measures

It is important for the historical images of the landscape, which represent a valuable cultural treasure, to be carefully preserved and made generally accessible. In order to achieve this objective, swisstopo will be intensifying the cataloguing and digitisation of the historical images during the next few years. In this way it will be possible to minimise the degree of use of the originals, which accelerates the natural deterioration process to which the analogue images are already susceptible due to ageing. In addition, digital geo-referenced aerial photo data will enable users to access the image material more quickly and conveniently.

Timetable and stages

swisstopo plans to digitise the entire inventory of images and make them generally accessible in the medium term. But in view of the magnitude of this undertaking, the various sections will have to be processed in separate stages. For this purpose, prioritisation is based on the careful weighing up of criteria such as current condition of the images, historical and cultural value, comprehensiveness of the products, and clients’ needs. The processing of an inventory of aerial images dating from the period from 1946 to 1972 that are in grave danger of deterioration (acetate and nitrate negatives) is the most urgent requirement.

In a report prepared in summer 2007 on the conservation of inventories of images at swisstopo, a variety of potential acute and latent forms of damage were identified, and appropriate measures were proposed. For the preservation of acetate and nitrate negatives dating from the period from 1946 to 1972 that were found to be particularly susceptible to deterioration, the management of swisstopo approved the necessary funding in spring 2008 in view of the urgent need for action. For the other inventories, swisstopo submitted an application to the federal government for additional financing, which was approved in spring 2009. The action plan for the preservation of inventories at swisstopo can therefore be implemented on a step-by-step basis. 

Specific measures

Archived images are susceptible to age-related deterioration processes. Nitrate negatives become self-igniting as degradation increases, and the nitrous gases that are released with ageing react with humidity to form nitric acid and can attack nearby images. Acetate negative films release acetic acid, which causes the film to shrink and the layer containing the image to decompose. In the case of glass negatives, silvering often occurs, and this can result in separation of layers. With colour slides, some colours can bleach more quickly than others, depending on the production method, and this can cause colour distortion.


Federal Office of Topography swisstopo Seftigenstrasse 264
P.O. Box
3084 Wabern
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+41 58 469 01 11

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Topography
Geodata Distribution
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Federal Office of Topography swisstopo

Seftigenstrasse 264
P.O. Box
3084 Wabern

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